Rating

After launching its first 45nm Phenom II processors in January, AMD has kept up the momentum, adding five new CPUs to the line-up. The new launches won't change the world - in terms of clock speed, they slot in below those previous 2.8GHz and 3GHz parts.

But they're the company's first processors to use its new Socket AM3 platform. AM3 isn't a break with the past like Intel's Core i7. Architecturally, it's very similar to the existing AM2 platform, and indeed the new chips can be used in existing Socket AM2 motherboards.

However, AM3 motherboards won't accept older processors that were designed for AM2. To prevent accidents, AM3 chips and sockets use only 938 pins: a 940-pin AM2 chip won't physically fit in the socket.

AM3 offers just one benefit over AM2, but it's a big one: it brings DDR3 memory support to the AMD platform, which until now has been DDR2-only. The newer technology offers only small performance benefits, but adoption is accelerating, and it's projected to become the dominant - and cheapest - RAM type by early 2010.

AMD envisages upgraders dropping a new AM3 processor into existing DDR2 systems, then upgrading to a DDR3 motherboard when prices fall. Beyond that, it's business as usual. The first Socket AM3 board we've seen (an Asus M4A79T) uses the same 790FX chipset and HyperTransport 3 bus as many existing AM2+ motherboards. Only the four DDR3 slots - and the so-subtly changed CPU socket - are anything new.

The new chips in depth

The five new processors occupy the lower end of the Phenom II range. Three new quad-core parts - the Phenom II X4 805, X4 810 and X4 910 - are accompanied by the first triple-core Phenoms, the X3 710 and X3 720.

These names reflect a new naming strategy. 900-series Phenom IIs are quad-core models with 6MB of L3 cache, as with the X4 920 and X4 940 that emerged last month, while 800-series models are quad-cores with only 4MB of L3.

|Confusingly, though, you may see retailers advertise the quad-core models as having 8MB and 6MB caches respectively, figures obtained by adding in the 2MB of L2 cache that's standard for all quad-core Phenoms.

Finally, the 700-series numbers denote triple-core chips. These have the larger 6MB L3 cache, but as with previous triple-core Phenoms, L2 cache is proportionately shrunken compared with the X4s, at 1.5MB rather than 2MB.

The last two digits of the model number convey relative clock speed, with five units translating to a speed gap of 100MHz. Thus, the X4 910 is a 2.6GHz part with 6MB of L3, while the X4 810 and 805 have smaller 4MB L3 caches and clock speeds of 2.6GHz and 2.5GHz respectively. The X3 710 and 720 run, predictably, at 2.6GHz and 2.8GHz.

Benchmark results

As we went to press, samples of the X4 910 had yet to materialise; but the other new arrivals achieved very respectable benchmark scores.

Clearly, the new architecture gives a real, if not earth-shattering, performance boost over AM2.In our initial tests, the 2.8GHz X4 920 in a Socket AM2 board with 2GB of DDR2 RAM achieved a benchmark of 1.62 - roughly on a par with Intel's Core 2 Duo E8500. This month, the X4 810 running with DDR3 on our AM3 board achieved an identical score, despite its smaller L3 cache and lower 2.6GHz clock-speed.

The 2.8GHz X3 720, tested in the same board, did even better than the X4 920, achieving an overall score of 1.65 despite being a core down.

Although the benefits of AM3 are clear, not all of the tests in our benchmark suite derived the same benefit. The X4 810 lagged a few per cent behind the X4 920 in our Office, Encoding and Multitasking tests, but made it up in our 2D Graphics test, scoring 1.89 against the 920's 1.81.

For the X3, running at the same frequency as the X4 920, it was the opposite story: 2D Graphics was its weakest suit, with a score of 1.78, while in every other test the chip equalled or bettered its quad-core counterpart.

AMD also promises that the new models will have considerable headroom for overclocking. In our tests with the Phenom II X4 940, we were able to increase performance by around 20% using stock cooling.

Bang per buck

Prices for X4 910 and 805 chips aren't yet confirmed, but the 810 should cost around $300, matching Intel's Core 2 Duo E8500 in both price and performance. With twice as many cores, it could be the more future-proof choice.

The real bargains are the X3 710 and 720, at $212 and $246 respectively. Their performance matches high-end Core 2 Duo chips, but they're cheaper and offer an extra core for multithreaded applications.

If you're upgrading a creaking Athlon system, it will be an attractive drop-in upgrade - just check your BIOS can support an AM3 processor before splashing out.

Benchmark table

This Review appeared in the May, 2009 issue of PC & Tech Authority Magazine

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